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About twice as many patients were admitted to hospitals in France for COVID-19 during a 2-month period than were admitted for seasonal influenza during a 3-month period the previous year, according to a study published online in The Lancet Respiratory Medicine.
In-hospital mortality was nearly three times higher for COVID-19 than for seasonal influenza, researchers found. In addition, patients with COVID-19 were more likely to require invasive mechanical ventilation (9.7% vs 4%) and had longer average ICU stays (15 days vs 8 days).
“SARS-CoV-2 appears to have a higher potential for respiratory pathogenicity, leading to more respiratory complications in patients with fewer comorbidities, and it is associated with a higher risk of mortality, particularly in adolescents, although any conclusions for this age group must be treated with caution considering the small number of deaths,” write Lionel Piroth, MD, PhD, from the Infectious Diseases Department, Dijon University Hospital, Dijon, France, and colleagues.
The study “is the largest to date to compare the two diseases and confirms that COVID-19 is far more serious than the flu,” study author Catherine Quantin, MD, PhD, said in a news release. “The finding that the COVID-19 death rate was three times higher than for seasonal influenza is particularly striking when reminded that the 2018/2019 flu season had been the worst in the past five years in France in terms of number of deaths,” continued Quantin, who jointly led the research. She is affiliated with the University Hospital of Dijon and Inserm.
The investigators analyzed data from a national database and compared 89,530 COVID-19 hospital admissions between March 1 and April 30, 2020, with 45,819 seasonal flu hospital admissions between December 1, 2018, and February 28, 2019.
The death rate was 16.9% among patients hospitalized with COVID-19, compared with 5.8% among patients hospitalized with influenza.
Fewer patients younger 18 years were hospitalized with COVID-19 than with seasonal influenza (1.4% vs 19.5%; 1227 vs 8942), but a larger proportion of those younger than 5 years required intensive care for COVID-19 (2.9% vs 0.9%). The fatality rates in children younger than 5 years were similar for both groups (0.5% vs 0.2%).
Among patients aged 11–17 years, 5 of 548 (1.1%) patients with COVID-19 died, compared with 1 of 804 (0.1%) patients with flu.
Testing practices for influenza likely varied across hospitals, whereas testing for COVID-19 may have been more standardized. This could be a limitation of the study, the researchers note. In addition, flu seasons vary year to year, and influenza cases may depend on vaccination coverage and residual population immunity.
“The large sample size is an important strength of the study and it is assumed that the indication for hospital admission in the two periods was the same and thus does not bias the results,” write Eskild Petersen, MD, DMsc, in a comment accompanying the study. “The results…clearly show that COVID-19 is more serious than seasonal influenza.”
Furthermore, this study and prior research show that “COVID-19 is not an innocent infection in children and adolescents,” said Petersen, who is affiliated with the University of Aarhus in Denmark and the European Society for Clinical Microbiology and Infectious Diseases Emerging Infections Task Force.
The study was funded by the French National Research Agency. Two authors have various financial ties to several pharmaceutical companies, details of which are available in the journal article. Petersen has disclosed no relevant financial relationships.